The need for improved illumination sources used for characterization of ever-shrinking integrated circuit device features continues to grow. One such illumination source includes a laser-sustained plasma (LSP) source. Laser-sustained plasma light sources are capable of producing high-power broadband light. Laser-sustained light sources operate by focusing laser radiation into a gas volume in order to excite the gas, such as argon or xenon, into a plasma state, which is capable of emitting light. This effect is typically referred to as plasma “pumping.” In typical LSP sources, pump light is focused to a single point. In the case where pumping light is focused to a single point, the laser intensity is the highest in a small region of space surrounding the focal point. The plasma shaping options are limited to the direction and numerical aperture (NA) of the laser focused to this point.
As shown in FIG. 1A, when the plasma 12 is pumped longitudinally, where the laser pump light 14 has a low NA, the shape of the plasma 12 for larger pump powers becomes elongated along the laser beam 14, 16 for larger pump powers. Typically, in settings where longer plasmas are desired, lower NA light or higher pump laser power is required. Further, once the given plasma grows into the region of low pump field gradient, plasma instabilities may occur. Therefore, it is desirable to provide a system and method which cures the deficiencies described above in the prior art.